1. Field of the Invention
This invention relates to a projecting exposure apparatus. This invention particularly relates to a projecting exposure apparatus, wherein an image of a two-dimensional pattern of light having been obtained from spatial light modulation is projected through an image side telecentric image forming optical system onto a photosensitive material, and the photosensitive material is thus exposed to the two-dimensional pattern of the light.
2. Description of the Related Art
Projecting exposure apparatuses, wherein spatial light modulation means for performing spatial light modulation of incident light is utilized, a two-dimensional pattern of the light, which has been obtained from the spatial light modulation performed by the spatial light modulation means, is projected onto a photosensitive material, and the photosensitive material is thus exposed to the two-dimensional pattern of the light, have heretofore been known. Also, projecting exposure apparatuses, wherein a digital micromirror device (hereinbelow referred to as the DMD) comprising a plurality of (e.g., 1,024×756) micromirrors, which allow alteration of their inclination angles and which are arrayed in a two-dimensional pattern, is utilized as the spatial light modulation means, have heretofore been known. (The projecting exposure apparatuses, wherein the digital micromirror device (DMD) is utilized as the spatial light modulation means, are described in, for example, Patent Literature 1.) As the digital micromirror device (DMD), for example, a DMD supplied by Texas Instruments Co. has been known. Projectors for dynamic images, wherein the DMD is utilized, and the like, have been used in practice.
The projecting exposure apparatuses utilizing the DMD are provided with an image forming lens for forming an image of each of the micromirrors of the DMD on the photosensitive material. With the projecting exposure apparatuses utilizing the DMD, the images of only the light, which has been reflected from certain micromirrors inclined at predetermined angles among the micromirrors that receive the irradiated light for exposure, and which travels toward the image forming lens, are formed through the image forming lens and on the photosensitive material. In this manner, the two-dimensional pattern having been obtained from the spatial light modulation performed by the DMD is projected onto the photosensitive material, and the photosensitive material is thus exposed to the two-dimensional pattern. Specifically, with the projecting exposure apparatuses utilizing the DMD, the exposure operation is performed such that each of pixels constituting the image of the two-dimensional pattern projected onto the photosensitive material corresponds to one of the micromirrors.
Also, attempts have heretofore been made to expose a photosensitive material, for example, a board on which a photoresist has been overlaid, to light carrying a circuit pattern by use of the projecting exposure apparatuses described above. Further, it has been considered to employ a technique, wherein an image forming optical system, which is telecentric on the image side, is utilized as the image forming optical system of the projecting exposure apparatuses, such that the image of the circuit pattern is capable of being formed on the board with accurate magnification, i.e. with quality free from variation in size of the image of the circuit pattern and distortion of the image.
[Patent Literature 1]                Japanese Unexamined Patent Publication No. 2001-305663        
However, at the time of the exposure operation for the circuit pattern described above, it is necessary to perform an adjustment of a focusing point such that the position of the formation of the image of the circuit pattern performed by the image forming optical system and the position of the photoresist layer overlaid on the board may coincide with each other. It may be considered that the adjustment of the focusing point be performed with, for example, an adjustment of an axial air separation between the lenses constituting the image forming optical system. However, it is not always possible to alter the axial air separation between the lenses constituting the image forming optical system such that the size of the image of the circuit pattern may not vary and such that the image of the circuit pattern may not be distorted. Therefore, it is desired that the adjustment of the focusing point is capable of being performed with an adjustment of the separation between the image forming optical system and the board provided with the photoresist layer.
However, for example, in cases where the exposure operation is to be performed for a base plate for the formation of a liquid crystal display panel, a base plate for the formation of a plasma display panel, or the like, which base plate has a comparatively large size, the size of the image forming optical system, or the like, becomes large as the size of the base plate subjected to the exposure operation becomes large, and the problems occur in that it is not always possible to alter the separation between the image forming optical system and the base plate in order to perform the adjustment of the focusing point. Also, for example, in cases where subregions of the entire region of the base plate are to be subjected successively to the exposure operation, while the base plate is being conveyed, and the exposure operation is thus performed for the entire exposure region, it is required that a shift in focusing point, which shift occurs due to warpage of the shape of the base plate (e.g., the warpage of the shape of 100 μm), or the like, be compensated for quickly in each of steps of the conveyance of the base plate. Therefore, the problems occur in that it is not always possible to alter the separation between the image forming optical system and the base plate in order to perform the adjustment of the focusing point.